The invention relates to a switching circuit with a time delay device the output signal of which actuates a load, such as a regulating device, with a delay relative to an input control signal.
Conventional switching arrangements of such character operate with electrical RC time delay devices. The timed intervals which are achievable with such conventional time delay deevices are rather limited because the RC timing network requires the use of very large capacitors for timing long intervals. Not only are large capacitors expensive and bulky but they have rather pronounced tolerances which lead to inaccuracy in timing. Such conventional switching arrangements using such RC time delay circuits are incapable of furnishing precisely and uniformly timed intervals in excess of one minute.
It is also known to equip or control switching elements with a bimetallic timing pulse generator. However, this entails substantial expenditures for the construction of such arrangement and requires a large amount of space. Moreover, the accuracy is unsatisfactory, response time is slow and operation of the timing feature is influenced by the environment in which the apparatus is operated.